Water / Decay - Water concentrations must be proper
for the decay process to develop. Microorganisms cause decayed wood, not
water. Portions of the old theory of spontaneous generation are still with
us. People still think that water causes wood to rot. The organisms that do
cause rot have very exacting requirements for water. If the amount of water in
the wood is too high or too low, the organisms will not grow and rot the wood.
The decay-causing organisms are obligatory aerobes, which means they must have
free oxygen for their growth. When a cavity fills with water, growth of
decay-causing organisms stops. When moisture concentration decreases to a
point below the fiber saturation point of wood, growth of most decay- causing
organisms stops. There are always exceptions to nature's rules. But, for the
most part, most decay-causing organisms grow best where the moisture content of
the wood is high, but where there is still free oxygen. It takes a relatively
long period to reach such a point where the wood begins to separate and oxygen
and moisture are available for the organisms. But, once the point is reached,
the decay can spread rapidly. Water is also required for the so-called dry
rot. The organisms that cause dry rot alter the wood in such a way that
moisture accumulates in it. Then the fungi use the water as they grow into new
wood surrounding the wet spot. When the moisture is gone, the growth of the
fungi stop. But, now a greater volume of altered wood is ready to accept more
water for the next period of growth. The concentration of water in wetwood is
not the only factor that holds back the growth of decay-causing fungi. Wetwood
has a very low amount of free oxygen and a very high pH which are factors that
hold back growth of decay-causing fungi.